35
12.3
SEQUENCE OF OPERATION
OPERATION
DISPLAY
1.
Upon a call for heat, the control turns on the appropriate
pumps.
WHR: Standby
OUT: 61.4C (65)
2.
The control connects 230 VAC to the fan. The fan does
not run at this time.
If the unit is equipped with a flow switch or low
water cut-off, it must close before the control
powers up the fan.
If the unit is equipped with a manual reset high limit
it must be closed before the control powers up the
fan.
If the unit is equipped with a solenoid valve and/or a
vent valve, they will be energized along with the fan.
If the unit is equipped with a gas pressure switch, it
must close at this time.
If there is an auxiliary device connected to the unit,
the unit will then provide 24 VAC to its enable relay.
If the auxiliary device has a proving switch, it must
close before the sequence continues.
WHR: Standby
OUT: 61.4C (65)
3.
The control then starts a 10 second pre-purge cycle.
WHR: PREPURGE
OUT: 61.5C (65)
4.
Once the pre-purge cycle is complete, and the blocked
drain and auto-reset high limit are closed, the control
starts the 5-second trial for ignition by sending spark
voltage to the ignition electrode and opening the gas
valve.
WHR: IGNITION
OUT: 61.5C (65)
5.
If the control does not detect flame by the end of the trial
for ignition, the control performs a 10 second postpurge.
On the EKW45CE to EKW115CE models, the control will
perform another prepurge and will try to light the burner
again. If the burner does not light after 4 trials, the control
will lockout for 1 hour and then try another set of 4 trials.
On the EKW145CE to EKW235CE models the unit will
lockout until manually reset.
WHR: POSTPURGE, PREPURGE
OUT: 61.5C (65)
6.
If the control detects a flame before the trial for ignition
ends, it begins to modulate the burner in order to maintain
the set point.
WHR: RUN 20% RATE
OUT: 62.6C (65)
7.
Once the call for heat is satisfied, the control will turn off
the burner. The fan will remain on for the 10-second
post-purge cycle. The primary pump will continue to run
for its respective pump delay time, and then turn off.
WHR: POSTPURGE
OUT: 64.5C (65))
8.
Primary pump switches off.
WHR: Standby
OUT: 64.8C (65)
